1. Field of the Invention
The present invention relates to an apparatus for manufacturing semiconductor devices. More particularly, the present invention relates to a conditioner device that can maintain a polishing rate of a polishing pad at a sufficient level, and also to a chemical mechanical polishing (CMP) apparatus having the same.
2. Discussion of the Related Art
With the integration density of a semiconductor device increasing, a tiny scratch or defect imposed on a wafer during a CMP process is considered as one of the major factors that deteriorate the productivity and yield in manufacturing the semiconductor device. Especially in the recent semiconductor manufacturing processes which uses large diameter wafers, for example, wafers of about 300 mm in diameter, the size of a polishing pad becomes larger with the increased size of the wafer. Accordingly, the stress and impact imparted on the surface of the wafer and the polishing pad during the CMP process are increasing, and in turn scratches or defects on the wafers are occurring more frequently.
The CMP process, as is well known in the field of this art, is for polishing the wafer with a polishing pad while simultaneously supplying a slurry to the wafer which is to be planarized. The slurry, byproducts of the polishing process, and various kinds of contaminants are deposited on the polishing pad during the CMP process, lowering the conditioning efficiency. To prevent this problem, a conditioner device is typically used. The conditioner device carries out a conditioning process for the polishing pad, it maintains the surface condition of the polishing pad at a constant level.
FIG. 1 illustrates the surface of the polishing pad of the conventional CMP apparatus. Referring to FIG. 1, the conventional conditioner device 10 includes (artificial) diamond particles distributed on a plurality of conditioning zones 12. The support plate 11 is partitioned into many conditioning zones 12. For example, about 50,000 to 60,000 artificial diamonds having diameters of about 110 μm are distributed at a separation distance of about 300 μm on the conditioner device 10. The gaps between the conditioning zones 12 are about 1.5 mm, and the diameter of the center area is about 10 mm, and the width of the peripheral area where no diamonds is about 6 mm.
Various kinds of slurries are used for the CMP process. The slurry can be strong acid or a strong alkali, containing different amounts of polishing particles. The lifetime of the conditioner device tends to be determined by the types of the slurries.
For instance, referring to Table 1 below, the lifetime of the conditioner device is different, depending on the type of the polished material layer and the slurry, even though the polishing pad and the conditioner device are the same.
TABLE 1Life Time of Conditioner DeviceCMP processSlurry(hours)Oxide CMPSilica25~35Oxide CMPCeria25~50Tungsten CMPTungstenBelow 20
Referring to FIG. 2, after 20 hours of usage, the conditioning capability or conditioning efficiency of the polishing pad has decreased by about 30% from the initial value for the ceria slurry (B) and the silica slurry (C), whereas the decrease is more than 70% for the tungsten slurry (A).
Referring to FIG. 3, as described above, about sixty thousands diamond particles 13, having diameters of about 100 μm, are attached to the circular support plate 13 by the layer of an adhesive 11a, the diamond particles being separated by a distance of about 300 μm from one another. The mobility of the slurry 14 is very low between the closely spaced diamond particles 13. Since the area between the plate 11 and the pad 15 not containing the diamond particles 13 is narrow, it is difficult for the slurry 14 to flow into and away from the conditioner device 10. When the number of the diamond particles 13 distributed on the conditioner device 10 is increased, the conditioning efficiency of the polishing pad 15 is better for the initial period of the usage. However, when the separation distances between the diamond particles 13 are closer, the mobility of the slurry 14 is reduced, and the diamond particles 13 erode more quickly.
As explained above, the slurry remaining in the conditioner device abrades the diamond particles. Especially, the abrasion of the diamond particles becomes a much more serious problem for the tungsten slurry that carries the chemicals of a strong acid and the polishing particles of which hardness being no less than that of the diamond particles. It is considered that this explains why the conditioning efficiency to the polishing pad in the CMP process decreases much more quickly for the tungsten than for the silica or ceria slurry. The decrease of the conditioning efficiency to the polishing pad causes many problems such as shortening the lifetime of the conditioner device, deteriorating the reliability of the polishing process, and increasing the process time.